The present disclosure relates to a light emitting diode (LED) driving apparatus capable of driving a light emitting diode directly, using alternating current (AC) power.
Light emitting diodes (LEDs), a semiconductor devices having a p-n junction structure and emitting light through the recombination of electrons and holes, has recently been applied to various technological fields in accordance with the development of semiconductor technology. Particularly, since LEDs have higher degrees of efficiency, longer effective lifespans and are more environment-friendly than existing light emitting devices, fields to which LEDs are applied have continuously increased.
Generally, LEDs are driven by direct current (DC) power having a level of several volts applied thereto in view of a structure thereof. Therefore, generally, in order to drive LEDs with commercially available alternating current (AC) power used domestically, commercially or industrially, a separate unit is required. In order to drive an LED with commercial AC power, an LED driving apparatus generally includes a rectifying circuit, an AC to DC converter, and the like.
However, since a general AC to DC converter has a relatively large volume and consumes a significant amount of power, when such a general AC to DC converter is used, advantages of LEDs such as high efficiency, a small packaging size, a long lifespan, and the like, are offset.
Therefore, a large amount of research into apparatuses capable of driving LEDs directly with AC power, without the need for an AC to DC converter, has recently been undertaken.
In an AC direct driving type LED driving circuit in which an LED is directly driven with AC power, a smoothing capacitor is not used, such that the LED driving circuit has advantages in terms of a lifespan, a size, and the like.
In the case of driving an LED directly with AC power, without the use of an AC to DC converter, a plurality of switches are connected to a plurality of LEDs, respectively, and corresponding LED groups are driven while being turned on or off depending on a level of the AC power. That is, an AC direct driving type LED driving circuit may control the LED groups to be automatically turned on or off depending on a change in an AC power voltage.
Meanwhile, in the AC direct driving type LED driving apparatus, a flicker phenomenon may occur due to noise in an AC power voltage at a boundary at which the number of LED groups that are turned on is changed.
Patent Documents 1 to 6, listed below, do not disclose a configuration for preventing a flicker phenomenon due to noise in an AC power voltage at a boundary at which the number of LED groups that are turned on is changed.